1. Field of the Invention
The present invention relates to a method and apparatus for evaluation of temporal and spatial variation of illumination in automated machine vision instruments. More specifically, the evaluation is conducted to characterize variations in global illuminance, static field intensity, dynamic field intensity, strobe repeatability, and intensity due to factors such as, for example, specimen thickness and cleanliness of system calibration hardware. Still more particularly, the present invention relates to automated instruments used for analyzing biological or cytological specimens, such as sputum samples, urine samples or pap smears.
2. Discussion of the Prior Art
Automated analysis of biological specimens requires a high degree of spatial and temporal uniformity for accurate and repeatable evaluation. Those evaluations often measure photometric properties such as nuclear and cytoplasm optical density. In order to accurately and repeatably measure these properties, the illumination must maintain a high degree of uniformity across the field of view and from collected image to collected image. In addition, morphological operations are conducted to segment various objects in the field of view for further analysis to determine various feature values related to size, shape and frequency content, among other factors. Operations used in such analyses tend to exhibit nonlinear behavior due to various thresholding schemes that may be employed. Therefore, accurate and repeatable behavior of these processing methods also necessitates a high degree of uniformity across each field of view and from collected image to collected image.